JP3616339B2 - 2-cycle internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-cycle internal combustion engine used for, for example, a portable power working machine, and in particular, to reduce the amount of air-fuel mixture discharged without being subjected to combustion, so-called blow-through amount, as much as possible. Therefore, the air is introduced into the combustion working chamber (also called the combustion chamber, working chamber, cylinder chamber, etc., but these are collectively referred to as the combustion working chamber) prior to the air-fuel mixture. The present invention relates to a two-cycle internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventional two-cycle gasoline engines used in portable power working machines such as brush cutters and chain saws are usually provided with a spark plug at the cylinder head, An intake port, a scavenging port, and an exhaust port that are opened and closed by a piston are formed, and there is no independent stroke only for intake and exhaust, and one cycle of the engine is completed in two strokes of the piston.
[0003]
More specifically, the air-fuel mixture is drawn from the intake port into the crank chamber below the piston by the upward stroke of the piston, and the air-fuel mixture is pre-compressed by the downward stroke of the piston, and the pre-compression is discharged from the scavenging port. Blowing the compressed air-fuel mixture into the combustion working chamber above the piston discharges the combustion waste gas to the exhaust port, in other words, scavenging the combustion waste gas using the gas flow of the air-fuel mixture In view of this, the unburned air-fuel mixture is likely to be mixed into the combustion waste gas (exhaust gas), and the amount of air-fuel mixture discharged to the atmosphere without being used for combustion, the so-called blow-through amount is large. Not only is the fuel efficiency worse than that of a cycle engine, but the exhaust gas contains a lot of harmful components such as HC (unburned component of fuel) and CO (incompletely burned component of fuel). Border pollution has been a concern.
[0004]
Therefore, conventionally, for example, an air introduction passage for introducing external air to the scavenging passage is provided, and air is introduced into the combustion working chamber prior to the air-fuel mixture in the downward stroke of the piston, thereby discharging the air. An air layer is formed between the combustion waste gas to be performed and the unburned mixture, and this air layer prevents the mixture and the combustion waste gas from being mixed, thereby reducing the amount of blow-through of the mixture. Various air-preceding (stratified scavenging) type two-cycle internal combustion engines that have been reduced have been proposed (for example, JP-A-9-125966, JP-A-5-33657, JP-A-3040758, etc.) See).
[0005]
Also, the applicant of the present invention has previously proposed a two-cycle internal combustion engine of the air advance introduction type having the basic configuration as shown in the following example (see Japanese Patent Application No. 2000-318841).
[0006]
In other words, the proposed one is a pair of schneille scavenging systems symmetrically across a longitudinal section that divides the exhaust port into two so as to communicate the combustion working chamber formed above the piston in the cylinder and the crank chamber. A plurality of pairs of scavenging passages are provided to guide air to the scavenging passages and to guide the air-fuel mixture to the crank chamber, and after the exhaust port is opened in the downward stroke of the piston, A scavenging port provided at a downstream end is opened, and the two-stroke internal combustion engine is configured to introduce air into the combustion working chamber through the scavenging passage in advance of the air-fuel mixture.
[0007]
In such a proposed two-cycle internal combustion engine, during the upward stroke of the piston, external air is sucked into the scavenging passage and the crank chamber through the air introduction passage and the air check valve interposed therein, and stored. In addition, the air-fuel mixture from the air-fuel mixture generating means such as a carburetor is sucked into the crank chamber and stored through the air-fuel mixture supply passage and the air-fuel mixture introduction port.
[0008]
When the air-fuel mixture in the combustion operation chamber above the piston is ignited and explodes, the piston is pushed down by the combustion gas. In the lowering stroke of the piston, the air and the air-fuel mixture in the scavenging passage and the crank chamber are compressed by the piston, and first, when the exhaust port is opened and the piston is further lowered, the downstream of the scavenging passage The scavenging port at the end is opened. In the scavenging period in which the scavenging port is opened, only the air compressed by the piston in the scavenging passage is first introduced into the combustion operation chamber from the scavenging port.
[0009]
Subsequently, when the piston is further lowered, the introduction of air from the scavenging port to the combustion working chamber is completed, and subsequently to the air, the air-fuel mixture precompressed in the crank chamber passes through the scavenging passage. It is introduced into the combustion working chamber until the scavenging period is completed.
[0010]
Accordingly, in the downward stroke of the piston, air is introduced from the scavenging port into the combustion working chamber in advance of the air-fuel mixture, so that this combustion air causes the combustion waste gas to be on the side opposite to the exhaust port. It is pushed out of the exhaust port and scavenged without remaining in the combustion working chamber, including the portion near the inner wall of the cylinder, and then discharged to the outside through the muffler.
[0011]
In this case, there is a layer of air introduced from the scavenging port into the combustion working chamber ahead of the scavenging port between the combustion waste gas and the air-fuel mixture introduced later from the scavenging port into the combustion working chamber. This air layer effectively prevents the air-fuel mixture from mixing with the combustion waste gas, enables stratified scavenging, and the amount of air-fuel mixture discharged without being used for combustion, so-called blow-through The amount can be reduced as much as possible, the ignition of the air-fuel mixture can be performed more reliably and completely, and the fuel consumption can be improved and harmful components in the exhaust gas can be reduced.
[0012]
[Problems to be solved by the invention]
However, in the conventional two-cycle internal combustion engine of the prior air introduction (stratified scavenging) proposed above, the effective passage sectional area of the crank chamber side end (upstream end = scavenging inlet) of the scavenging passage is generally substantially the same as the downstream side. Because it is equal or wider than the downstream side, the air-fuel mixture is likely to be mixed in the air introduced in advance into the combustion working chamber during the scavenging period (especially from the middle to the final stage), and the dislike of incomplete stratified scavenging was there.
[0013]
The present invention has been made to improve the above-mentioned problems, and the object of the present invention is to make it possible to perform complete stratified scavenging by making it difficult to mix the air-fuel mixture into the air introduced into the combustion working chamber in advance during the scavenging period. An object of the present invention is to provide a two-cycle internal combustion engine of the air advance introduction type.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the two-cycle internal combustion engine according to the present invention basically divides the exhaust port into two so as to communicate the combustion working chamber formed above the piston in the cylinder and the crank chamber. Take the Schnure scavenging system symmetrically across the longitudinal section Scavenging passage Is provided at the downstream end of the scavenging passage after the exhaust port is opened during the downward stroke of the piston. The scavenging port is opened, and air is introduced into the combustion working chamber through the scavenging passage in advance of the air-fuel mixture.
[0015]
And said A plurality of pairs of scavenging passages are provided, and each of the plurality of pairs of scavenging passages is provided with a throttle portion in the vicinity of the end portion on the crank chamber side, and each of the throttling portions is formed from a downstream portion of each of the scavenging passages. The effective passage cross-sectional area is made narrow and the effective passage cross-sectional areas are made substantially equal to each other so that the required amount of air-fuel mixture is fed into the combustion working chamber following the air. It is characterized by that.
In a preferred embodiment, the pair of scavenging passages are joined together on the crank chamber side to increase the volume thereof, and the crank passage is connected via a common restricting portion for narrowing the effective passage cross-sectional area from the downstream side. You can communicate with the room.
[0016]
In another preferred embodiment, an air introduction passage for introducing air into the scavenging passage is provided, and an air check valve is provided in the air introduction passage.
In this case, the volume of the scavenging passage is preferably set equal to or slightly smaller than the amount of air to be introduced in advance.
The effective passage cross-sectional area of the throttle portion is preferably set to a size that allows the air-fuel mixture to be fed into the combustion working chamber following the air by a required amount.
[0017]
In a preferred embodiment of the two-cycle internal combustion engine according to the present invention configured as described above, external air is supplied to the air introduction passage and the scavenging passage as the crank chamber becomes negative pressure in the upward stroke of the piston. The air-fuel mixture from the air-fuel mixture generating means such as a carburetor is supplied to the crank through the air-fuel mixture supply passage and the air-fuel mixture introduction port. Inhaled and stored in the chamber.
[0018]
When the air-fuel mixture in the combustion operation chamber above the piston is ignited and explodes, the piston is pushed down by the combustion gas. In the downward stroke of the piston, the air and the air-fuel mixture in the air introduction passage, the scavenging passage, and the crank chamber are compressed by the piston, the exhaust port is first opened, and the piston is further lowered. Then, the scavenging port at the downstream end of the scavenging passage is opened. In the scavenging period in which the scavenging port is opened, only the air compressed by the piston in the scavenging passage is first introduced into the combustion operation chamber from the scavenging port.
[0019]
Subsequently, when the piston is further lowered, the introduction of air from the scavenging port to the combustion working chamber is completed, and following the air, the air-fuel mixture precompressed in the crank chamber is provided with the throttle portion. The scavenging passage is introduced into the combustion working chamber until the scavenging period is completed.
[0020]
Accordingly, in the downward stroke of the piston, air is introduced from the scavenging port into the combustion working chamber in advance of the air-fuel mixture, so that this combustion air causes the combustion waste gas to be on the side opposite to the exhaust port. It is pushed out of the exhaust port and scavenged without remaining in the combustion working chamber, including the portion near the inner wall of the cylinder, and then discharged to the outside through the muffler.
[0021]
In this case, there is a layer of air introduced from the scavenging port into the combustion working chamber ahead of the scavenging port between the combustion waste gas and the air-fuel mixture introduced later from the scavenging port into the combustion working chamber. This air layer effectively prevents the air-fuel mixture from mixing with the combustion waste gas, enables stratified scavenging, and the amount of air-fuel mixture discharged without being used for combustion, so-called blow-through The amount can be reduced as much as possible, the ignition of the air-fuel mixture can be performed more reliably and completely, and the fuel consumption can be improved and harmful components in the exhaust gas can be reduced.
[0022]
In the two-cycle internal combustion engine of the present invention, a throttle portion is provided in the vicinity of the crank chamber side end (upstream end = scavenging inlet) of the scavenging passage, so that it is mixed with the air sucked into the scavenging passage. Air is hardly mixed, so that air is surely guided, and a more complete layered scavenging is possible.
[0023]
Further, since the throttle portion is present, the air-fuel mixture is introduced from the crank chamber into the scavenging passage after the pressure in the crank chamber increases to some extent. In other words, the time when the air-fuel mixture is introduced from the crank chamber into the scavenging passage is slightly delayed as compared with the case where the throttle portion is not provided, so that more complete stratified scavenging is possible.
[0024]
As a result, a more complete stratified scavenging can be performed, the amount of air-fuel mixture discharged without being subjected to combustion, the so-called blow-off amount can be greatly reduced, and ignition of the air-fuel mixture can be performed more reliably and completely. It is possible to further improve the fuel consumption and reduce harmful components in the exhaust gas.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a two-cycle internal combustion engine according to the present invention will be described with reference to the drawings.
1 is a longitudinal sectional view at the top dead center of a piston showing a first embodiment of a two-cycle internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along arrow II-II in FIG. 1, and FIG. 3 corresponds to FIG. FIG. 4 is a cross-sectional view taken along arrow IV-IV in FIG. 3.
[0026]
For convenience of explanation, the left side of the line FF in FIG. 2 is a longitudinal section passing through the first scavenging port at the bottom dead center of the piston, and the right side is passing through the second scavenging port at the top dead center of the piston. Longitudinal sections are synthesized and illustrated.
[0027]
A two-cycle internal combustion engine 1 of the illustrated embodiment is a four-flow scavenging type small air-cooled two-cycle gasoline engine used for a portable power working machine or the like, and has a cylinder 10 into which a piston 20 is inserted. A crankcase 12 having a left and right split configuration is fastened in a sealed state by four through bolts 27 (see FIG. 4) passed through the four corners. The crankcase 12 defines a crank chamber 18 below the cylinder 10 and rotatably supports a crankshaft 22 that reciprocates the piston 20 via a connecting rod 24. 10 and the crankcase 12 constitute an engine body 2.
[0028]
A base part 13 of a recoil starter case and a base part 19 of a fan case are integrally provided at the left and right ends of the crankcase 12.
A large number of cooling fins 16 are provided on the outer peripheral portion of the cylinder 10, and a squish dome-shaped (hemispherical) combustion chamber portion 15 a constituting the combustion working chamber 15 is provided on the head portion thereof. A spark plug 17 is provided on the part 15a.
[0029]
Further, an exhaust port 34 is provided on one side (right side in FIG. 1) of the cylinder 10, and left and right with a longitudinal section FF (see FIG. 2) dividing the exhaust port 34 in two. Symmetrically, a pair of first scavenging passages 31, 31 positioned on the opposite side of the exhaust port 34, and a pair of second scavenging passages 32, 32 positioned on the exhaust port 34 side, which are of the Schnure scavenging type, , Is provided. At the upper ends (downstream ends) of the first scavenging passages 31 and 31 and the second scavenging passages 32 and 32, first scavenging ports 31a and 31a and second scavenging ports 32a that open to the combustion working chamber 15 are provided. 32a is provided.
[0030]
Here, the height positions of the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are the same, and the height positions of their upper ends are predetermined from the upper end of the exhaust port 34. The distance h is lowered (see FIG. 3). Accordingly, the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are opened at the same time in two pairs with a slight delay from the exhaust port 34 when the piston 20 descends. In addition, the outer peripheral side of said 1st and said 2nd scavenging passage 31, 31, 32, 32 is a pair of right and left attached to the plane parts 10b and 10b processed into the same plane of the wall part 10A outer periphery of the said cylinder 10. The lid-shaped members 60, 60 are closed (see FIG. 4).
[0031]
In the present embodiment, air A is supplied to the two pairs of scavenging passages 31, 31, 32, and 32 on the wall 10 </ b> A on the opposite side (left side in FIG. 1) of the cylinder 10 from the exhaust port 34. An air introduction passage 50 is provided.
[0032]
The air introduction passage 50 has an air introduction port 51 provided near the center in the height direction of the cylinder 10 and a pair of left and right linear branches that are connected to the air introduction port 51 at a predetermined crossing angle on the left and right. It comprises a passage portion 52, 52, and a pair of left and right communication portions 54, 54 communicating the branch passage portion 52, 52 and the first and second scavenging passages 31, 31, 32, 32. .
[0033]
The pair of left and right communication portions 54, 54 are formed by the lid-like members 60, 60 attached to the cylinder 10. The lid-shaped member 60 includes a passage forming portion 61 having a U-shaped cross section and a nine-shaped vertical cross section, and a blind lid member 63 that closes the opening side of the passage forming portion 61. An air inlet 55 is formed on the branch passage 52 side of the forming portion 61, an air outlet 56 is formed on the scavenging passages 31 and 32, and on the scavenging passages 31 and 32 side of the air outlet 56. An air reed valve 62 with a stopper as an air check valve is attached to open and close the air outlet 56.
[0034]
On the other hand, an air-fuel mixture inlet 30 that is opened and closed by the piston 15 is provided below the air inlet 51 in the cylinder 10, and a passage is provided in the air inlet 50 and the air-fuel mixture inlet 30. A vaporizer 40 as an air-fuel mixture generating means is attached via a heat insulator 45, and an air cleaner 46 is attached upstream of the vaporizer 40.
[0035]
Air A and air-fuel mixture M are supplied to the air inlet 51 and the air-fuel mixture inlet 30 via the air cleaner 46, the vaporizer 40, and the insulator 45.
[0036]
The vaporizer 40 includes an air supply passage 42 for guiding the external air A purified by the air cleaner 46 to the air introduction port 51, and the air-fuel mixture M generated by the vaporizer 40 as the insulator. 45 and an air-fuel mixture supply passage 41 that leads to the crank chamber 18 through the air-fuel mixture inlet 30 are provided adjacent to each other, and a link member (not shown) is provided in each of the air supply passage 42 and the air-fuel mixture supply passage 41. There are disposed throttle valves 44 and 43 that are linked to each other.
[0037]
In the two-cycle internal combustion engine 1 of the present embodiment in addition to the above-described configuration, as shown in FIG. 2, end portions on the crank chamber side 18 in the first scavenging passages 31, 31 and the second scavenging passages 32, 32. In the vicinity of (upstream end = scavenging inlet), throttle portions 31e, 31e, 32e, 32e are provided.
[0038]
Here, the volumes of the first scavenging passages 31 and 31 and the second scavenging passages 32 and 32 are substantially equal to each other, so that the outside air A is scavenged during the upward stroke of the piston 20. The passage 31, 31, 32, 32 is sucked into and filled with a small amount of air into the crank chamber 18, in other words, the amount of air to be introduced into the combustion working chamber 15 in advance. It is set to be equivalent or slightly smaller.
[0039]
The throttle portions 31e, 31e, 32e, and 32e are provided so that the effective passage cross-sectional area is narrower than the downstream portions of the first and second scavenging passages 31, 31, 32, and 32. The effective passage cross-sectional areas of 31e, 31e, 32e, and 32e are substantially equal to each other, and the required amount of the air-fuel mixture M follows the air A in the combustion working chamber 15 (a predetermined air-fuel ratio is obtained). (Size) is set to the size to be sent.
[0040]
In the two-cycle internal combustion engine 10 of the present embodiment configured as described above, during the upward stroke of the piston 20, the external air A is supplied to the air supply passage 42, the air introduction passage 50, and the air reed valve. 62 is sucked and stored in the first and second scavenging passages 31, 31, 32, and 32 (somewhat also enters the crank chamber 18 through the throttle portions 31 e, 31 e, 32 e, and 32 e), Further, the air-fuel mixture M from the carburetor 40 is sucked and stored in the crank chamber 18 through the air-fuel mixture supply passage 41 and the air-fuel mixture inlet 30 (see FIGS. 1 and 2). In this case, only the air A is filled in the first and second scavenging passages 31, 31, 32, 32, and the air-fuel mixture M does not enter at all.
[0041]
When the piston 20 rises and the compressed air-fuel mixture M in the combustion working chamber 15 is ignited by the spark plug plug 17 and explosively burns, the piston 20 is pushed down by the combustion gas. In the downward stroke of the piston 20, the scavenging passages 31, 31, 32, 32 and the air A and the air-fuel mixture M in the crank chamber 18 are compressed by the piston 20, and first, the exhaust gas is discharged. When the opening 34 is opened and the piston 20 is further lowered by the predetermined distance h, the first and second scavenging gas at the downstream ends of the first and second scavenging passages 31, 31, 32, 32. The mouths 31a, 31a, 32a, 32a are opened. In the scavenging period in which the scavenging ports 31a, 31a, 32a, and 32a are opened, first, the scavenging ports 31a, 31a, 32a, and 32a first pass through the first and second scavenging passages 31, 31, 32, and 32. Only the air A compressed by the downward stroke of the piston 20 is introduced into the combustion working chamber 15 in advance.
[0042]
Subsequently, when the piston 20 is further lowered, the introduction of the air A from the scavenging ports 31a, 31a, 32a, 32a to the combustion working chamber 15 is completed, and after the air A, in the crank chamber 18 The pre-compressed air-fuel mixture M is introduced into the combustion working chamber 15 through the first and second scavenging passages 31, 31, 32, 32 until the scavenging period is completed.
[0043]
Accordingly, in the downward stroke of the piston 20, air A is introduced into the combustion working chamber 15 from the scavenging ports 31a, 31a, 32a, 32a in advance of the air-fuel mixture M. The waste gas E is pushed out of the exhaust port 34 and scavenged without remaining in the combustion working chamber 15, including a portion near the cylinder inner wall opposite to the exhaust port 34, and then the muffler 90. It is discharged to the outside through.
[0044]
In this case, the scavenging ports 31a, 31a, 31a, 32a, 32a, and the air-fuel mixture M introduced behind the air A from the scavenging ports 31a, 31a, 32a, 32a, A layer of air A introduced into the combustion working chamber 15 in advance from 31a, 32a, 32a is formed, and this air A layer effectively prevents the mixture M from mixing with the combustion waste gas E. The stratified scavenging is possible, and the amount of air-fuel mixture discharged without being used for combustion, the so-called blow-through amount, can be reduced as much as possible, and ignition of the air-fuel mixture can be made more reliably and completely, improving fuel efficiency It is possible to reduce harmful components in the exhaust gas.
[0045]
In particular, in the two-cycle internal combustion engine 1 of the present embodiment, the throttle portions 31e, 31e, 32e, and 32e are provided near the ends (upstream ends) of the scavenging passages 31, 31, 32, and 32 on the crank chamber 18 side. Therefore, the air-fuel mixture M is hardly mixed with the air A sucked into the scavenging passages 31, 31, 32, 32. Therefore, the air A is surely guided, and a more complete layered structure is obtained. Scavenging is possible.
[0046]
Further, the presence of the throttle portions 31e, 31e, 32e, 32e allows the air-fuel mixture M to reach the scavenging passages 31, 31, 32, 32 from the crank chamber 18 after the pressure in the crank chamber 18 increases to some extent. Will be introduced. In other words, the timing when the air-fuel mixture M is introduced from the crank chamber 18 into the scavenging passages 31, 31, 32, 32 is slightly delayed as compared with the case where the throttle portions 31e, 31e, 32e, 32e are not provided. This allows for more complete stratified scavenging.
[0047]
As a result, a more complete stratified scavenging can be performed, the amount of air-fuel mixture discharged without being subjected to combustion, the so-called blow-off amount can be greatly reduced, and ignition of the air-fuel mixture can be performed more reliably and completely. It is possible to further improve the fuel consumption and reduce harmful components in the exhaust gas.
[0048]
Further, in addition to the above-described effects, in the two-cycle internal combustion engine 1 of the present embodiment, the air introduction passage 50 is provided in the wall portion 10A of the cylinder 10, so that the engine main body (cylinder and crank) is different from the conventional one. Compared to the case where a bifurcated air introduction passage that is separate from those is provided outside the case), the area around the engine can be gathered rationally and compactly, reducing the number of parts, reducing weight, Cost reduction, processing, improvement of assembly, etc. can be achieved.
[0049]
In this case, the pair of left and right branch passages 52 and 52 constituting the main part of the air introduction passage 50 are formed in a straight line, so that the branch passages 52 and 52 are formed not only by die cutting but also by drilling. Thus, the scavenging passages 31, 31, 32, 32 can also be formed by being covered with the lid-like member 60 as the outer peripheral side open molding, and the productivity is remarkably improved.
[0050]
Further, by providing the air introduction passage 50 in the wall portion 10A of the cylinder 10, it is possible to make the effective length of the air introduction passage 50 shorter than the conventional one, thereby improving the performance such as responsiveness. We can expect improvement.
Furthermore, since the air is supplied by piston pumping without using an external pump or the like, the structure is simplified and the manufacturing cost can be kept low.
[0051]
Next, another embodiment of the present invention will be described.
5 is a longitudinal sectional view showing a second embodiment of the two-cycle internal combustion engine according to the present invention, FIG. 6 is a sectional view taken along arrow VI-VI in FIG. 5, and FIG. 7 is a sectional view taken along arrow VII-VII in FIG. 8 is a cross-sectional view taken along arrow VIII-VIII in FIG.
[0052]
For convenience of explanation, the left side of the FF line in FIG. 6 is a longitudinal section passing through the first scavenging port side end at the bottom dead center of the piston, and the right side is the second scavenging at the top dead center of the piston. A longitudinal section passing through the mouth side end is synthesized and shown.
In each figure, the same reference numerals are given to portions corresponding to the respective portions of the first embodiment described above or the same functional portions.
[0053]
The two-cycle internal combustion engine 2 of the second embodiment shown in the figure is a four-flow scavenging type small air-cooled two-cycle gasoline engine used for a portable power working machine or the like, and includes a cylinder 10 into which a piston 20 is inserted and the piston 20. And a crankcase 12 that supports a crankshaft 22 that reciprocates up and down through a connecting rod 24. A large number of cooling fins 16 are provided on the outer periphery of the cylinder 10, and a squish dome-shaped (hemispherical) combustion chamber portion 15 a constituting the combustion working chamber 15 is provided on the head portion of the cylinder 10. A spark plug 17 is erected.
[0054]
Further, an exhaust port 34 is provided on one side of the cylinder 10 (on the right side in FIG. 5), and the combustion chamber 15 above the piston 20 and the crank chamber 18 are communicated with each other. A pair of first scavenging passages 31, 31 located on the opposite side of the exhaust port 34, which is symmetrically sandwiched with a longitudinal section F-F (FIG. 6) that divides the exhaust port 34 into two, and is of the Schnure scavenging type. And a pair of second scavenging passages 32 and 32 located on the exhaust port 34 side. First scavenging ports 31a and 31a that open to the combustion working chamber 15 are provided at upper ends (downstream ends) of the first scavenging passages 31 and 31, and upper ends (downstream) of the second scavenging passages 32 and 32 are provided. The second scavenging ports 32 a and 32 a that open to the combustion working chamber 15 are also provided at the end.
[0055]
Here, the height positions of the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are the same, and they are opened at the same time when the piston 20 is lowered.
The pair of first scavenging passages 31 and 31 and the second scavenging passages 32 and 32 are walled scavenging passages in which the combustion working chamber 15 side is closed by a cylinder inner wall.
[0056]
As can be understood by referring to FIGS. 7 and 8 in addition to FIGS. 5 and 6, the midstream portion of the pair of second scavenging passages 32 and 32 is substantially parallel to the first scavenging passages 31 and 31. Although extending vertically in the cylinder height direction, its upstream portion 32b (on the crank chamber 18 side) extends in an arc shape so as to surround the combustion working chamber 15 in a plane orthogonal to the midstream portion. The first scavenging passages 31 and 31 are combined at the upstream end of the crank chamber 18 located on the exhaust port 34 side, and the total length of the first scavenging passages 31 and 31 is increased. The volume of the passages 32 and 32 is considerably larger.
[0057]
Furthermore, a common throttle portion 32e ′ that makes the effective passage cross-sectional area narrower than the downstream side is provided at the upstream end portion of the second scavenging passage 32 that is located on the exhaust port 34 side on the crank chamber 18 side, The crank chamber 18 is communicated with the common throttle portion 32e ′.
Further, throttle portions 31e and 31e that make the effective passage cross-sectional area narrower than the downstream side are also provided at the ends of the first scavenging passages 31 and 31 on the crank chamber 18 side.
[0058]
A vaporizer 40 as an air-fuel mixture generating means is attached to the cylinder 10 on the side opposite to the exhaust port 34 (left side in FIG. 5) via a heat insulator 45 with a passage and a packing 49. An air cleaner 46 is attached to the upstream side of the vessel 40.
[0059]
The carburetor 40 is generated by the air supply passage (upstream portion) 42 for introducing the air A purified by the air cleaner 46 to the first and second scavenging passages 31, 31, 32, 32 and the carburetor 40. An air-fuel mixture supply passage (upstream portion) 41 that guides the air-fuel mixture M to the combustion operation chamber 15 is provided, and the air supply passage 42 and the air-fuel mixture supply passage 41 are linked to each other via a link member 45. Throttle valves 44 and 43 are provided.
[0060]
Here, the air supply passage 42 and the air-fuel mixture supply passage 41 are provided adjacent to each other in the vertical direction, and the downstream side of the air supply passage 42 is divided into two branches as can be understood with reference to FIGS. 6 and 7. The air introduction passage portions 42A and 42A are air outlet ports 36 and 36 at the downstream ends of the air introduction passage portions 42A and 42A, and the first scavenging passages 31 and 31 and the second scavenging passages 32 and 32, respectively. A check valve that prevents the air A from escaping to the air introduction passages 42A and 42A when the piston 20 is lowered is connected to the air outlets 36 and 36. Reed valves 52 and 52 with stoppers are respectively disposed.
[0061]
In the present embodiment, a single check valve (the reed valve 52) is shared for the first scavenging passage 31 and the second scavenging passage 32 for cost reduction. A check valve may be provided separately for each of the passages 31 and 32.
In addition, a reed valve 47 with a stopper as a check valve that prevents the air-fuel mixture M from flowing back to the vaporizer 40 side is also provided in the heat insulator 45 downstream of the air-fuel mixture passage 41. .
[0062]
In addition to the above, a communication passage 41A that connects the crank chamber 18 and the combustion working chamber 15 is provided at the downstream end of the air-fuel mixture supply passage 41, and the downstream end (upper end) of the communication passage 41A is connected to the piston. 20 is an air-fuel mixture supply port 33 that opens into the combustion working chamber 15 above, and is provided at the downstream end of the air-fuel mixture supply port 33 and the first and second scavenging passages 31, 31, 32, 32. The mixture M is blown out from the first and second scavenging ports 31a, 31a, 32a, 32a toward the combustion chamber 15a in the combustion working chamber 15, and further, the mixture passage 41 and the The air-fuel mixture M is also introduced into the crank chamber 18 through the crank chamber port 37 through the communication passage 41A.
[0063]
In the two-cycle internal combustion engine 2 of the second embodiment configured as described above, the external air A flows from the air passage 42 to the first scavenging passages 31 and 31 and the second scavenging during the upward stroke of the piston 20. The air is sucked and stored in the passages 32 and 32 (which also enters the crank chamber 18 through the throttle portions 31e, 31e, and 32e '), and the vapor mixture passage 41 and the crank chamber 18 contain the vaporization. The air-fuel mixture M from the container 40 is sucked and stored. In this case, only the air A is filled in the first and second scavenging passages 31, 31, 32, 32, and the air-fuel mixture M does not enter at all.
[0064]
When the air-fuel mixture M in the combustion working chamber 15 above the piston 20 is ignited and explosively burns, the piston 20 is pushed down by the combustion gas. In the downward stroke of the piston 20, the air A and the mixture M in the crank chamber 18, the first scavenging passages 31, 31, and the second scavenging passages 32, 32 are moved by the piston 20. First, when the exhaust port 34 is opened and the piston 20 descends, the first scavenging passages 31 and 31 and the second scavenging passages 32 and 32 are downstream of the first scavenging. The air ports 31a, 31a and the second scavenging ports 32a, 32a are opened simultaneously. In the initial stage of the scavenging period when the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are opened, the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a Only the air A compressed by the piston 20 in the scavenging passages 31 and 31 and the second scavenging passages 32 and 32 is introduced into the combustion working chamber 15.
[0065]
Subsequently, when the piston 20 is further lowered, the air A in the second scavenging passages 32, 32 is continuously introduced into the combustion working chamber 15 from the second scavenging ports 32a, 32a (scavenging period). In contrast, the introduction of the air A from the first scavenging ports 31a, 31a to the combustion working chamber 15 is completed. That is, since the volume of the second scavenging passages 32 and 32 is larger than the volume of the first scavenging passages 31 and 31, a period in which the first scavenging ports 31a and 31a start to open has elapsed. Then, all the air in the first scavenging passages 31 and 31 is introduced into the combustion working chamber 15 from the first scavenging ports 31a and 31a, and thereafter the first scavenging ports 31a and 31a. The air-fuel mixture M pre-compressed in the crank chamber 18 following the air A is introduced into the combustion working chamber 15 through the first scavenging passages 31 and 31 until the scavenging period is completed.
[0066]
Accordingly, in the downward stroke of the piston 20, air A precedes the air-fuel mixture M (indicated by solid arrows in FIGS. 5 and 7) from the first scavenging ports 31a and 31a to the combustion operation chamber 15. While being introduced, air A (indicated by a one-dot chain line arrow in FIGS. 5 and 7) from the second scavenging ports 32 a and 32 a to the combustion working chamber 15 over a longer period than the first scavenging ports 31 a and 31 a. A large amount will be introduced.
[0067]
In addition, after the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are opened, the piston 20 is further lowered, in other words, the first scavenging ports 31a, 31a and the second scavenging ports. The air mixture supply port 33 is opened slightly later than the scavenging ports 32a and 32a (for example, about 10 ° behind the crank angle), and the combustion chamber of the combustion working chamber 15 is opened from the air mixture supply port 33. A relatively rich mixture M (indicated by a solid arrow in FIGS. 5 and 7) in the mixture passage 41 (and in the crank chamber 18) is blown out toward the portion 15a until the scavenging period is completed. Rotate around the combustion chamber 15a.
[0068]
Conventionally proposed (for example, see Japanese Patent Application No. 11-134091), in a four-flow scavenging type two-stroke internal combustion engine in which the first scavenging port is dedicated to air and the second scavenging port is dedicated to air-fuel mixture, Although combustion waste gas tends to remain in a portion near the inner wall surface of the cylinder on the opposite side to the exhaust port, in the two-cycle internal combustion engine 2 of the present embodiment, the first scavenging port in the initial stage of the scavenging period. Since only air A is introduced into the combustion working chamber 15 from both the 31a, 31a and the second scavenging ports 32a, 32a, the combustion waste gas E (broken arrows in FIGS. 5 and 7) is generated by the air A. The muffler including the portion near the inner wall of the cylinder opposite to the exhaust port 34 is pushed out to the exhaust port 34 and is scavenged with little remaining, and then a muffler with a built-in exhaust purification device. It is discharged to the outside through the 0.
[0069]
In this case, between the combustion waste gas E and the air-fuel mixture M that is introduced into the combustion operation chamber 15 from the air-fuel mixture supply port 33 and the second air scavenging ports 32a and 32a, the first sweeping is performed. A layer of air A introduced into the combustion working chamber 15 in advance from the air ports 31a, 31a and the second scavenging ports 32a, 32a is formed, and the air-fuel mixture M is converted into combustion waste gas E by the layer of air A. Mixing is effectively prevented, and almost complete laminar scavenging is possible.
[0070]
That is, in the two-cycle internal combustion engine 2 of the present embodiment, the second scavenging passages 32 and 32 are substantially used as air passages, and the first scavenging passages 31 and 31 are for air at the beginning of the scavenging period. However, after that, the air-fuel mixture supply port 33 is opened as a passage for the air-fuel mixture, and is slightly delayed from the first gas scavenging ports 31a and 31a and the second gas scavenging ports 32a and 32a. From the middle of the period, a relatively rich air-fuel mixture M is blown out from the first scavenging ports 31a, 31a and the air-fuel mixture supply port 33 toward the combustion chamber portion 15a of the combustion working chamber 15, The air-fuel mixture M blown out is effectively prevented from being mixed with the combustion waste gas E by the previously introduced layer of air A and is swirled in the vicinity of the combustion chamber 15a. Almost perfect stratified flame The amount of air-fuel mixture discharged without being used for combustion, the so-called blow-through amount, can be reduced as much as possible, and the air-fuel mixture can be ignited more reliably and completely. Reduction of harmful components can be achieved.
[0071]
In the two-cycle internal combustion engine 2 of the second embodiment as well, as in the first embodiment, the throttle portion 31e is located near the end of the scavenging passages 31, 31, 32, 32 on the crank chamber 18 side. , 31e and 32e ′ are provided, so that the air-fuel mixture M is hardly mixed with the air A sucked into the scavenging passages 31, 31, 32 and 32, and therefore the air A is surely guided. And more complete stratified scavenging is possible.
[0072]
Further, since the throttle portions 31e, 31e, and 32e ′ are present, the air-fuel mixture M enters the scavenging passages 31, 31, 32, and 32 from the crank chamber 18 after the pressure in the crank chamber 18 increases to some extent. Will be introduced. In other words, the timing when the air-fuel mixture M is introduced from the crank chamber 18 into the scavenging passages 31, 31, 32, 32 is slightly delayed as compared with the case where the throttle portions 31e, 31e, 32e ′ are not provided. This allows for more complete stratified scavenging.
[0073]
As a result, a more complete stratified scavenging can be performed, the amount of air-fuel mixture discharged without being subjected to combustion, the so-called blow-off amount can be greatly reduced, and ignition of the air-fuel mixture can be performed more reliably and completely. It is possible to further improve the fuel consumption and reduce harmful components in the exhaust gas.
[0074]
Further, since the air passage 42 and the air-fuel mixture passage 41 are provided next to each other, etc., the engine surroundings can be rationally and compactly assembled, and can be easily mounted on a portable power working machine or the like.
Furthermore, since the air supply is performed by piston pumping without using an external pump or the like, the structure becomes simple and the manufacturing cost can be kept low.
[0075]
As described above, the two embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and in the design without departing from the spirit of the invention described in the claims, Various changes can be made.
[0076]
For example, in the two embodiments, the height positions of the first scavenging ports 31a, 31a and the second scavenging ports 32a, 32a are the same, and they are substantially the same when the piston 20 is lowered. Although it is made to open, the height position of said 1st scavenging port 31a, 31a and said 2nd scavenging port 32a, 32a does not necessarily need to set the same, and may give them a height difference. . In addition to the height position, the shape, opening area, horizontal scavenging angle, and the like of the first scavenging ports 31a and 31a and the second scavenging ports 32a and 32a enable stratified scavenging and residual combustion. Any setting may be used as long as the scavenging effect of the waste gas E can be enhanced.
[0077]
Further, the volume of the first scavenging passages 31, 31 and the second scavenging passages 32, 32, the effective passage cross-sectional area of the throttle portions 31 e, 31 e, 32 e, 32 e, 32 e ′, etc. It can be set as appropriate in consideration of the target air-fuel ratio of the air-fuel mixture M to be used for combustion.
[0078]
【The invention's effect】
As understood from the above description, according to the present invention, the throttle portion is provided in the vicinity of the end of the scavenging passage on the crank chamber side, so that the air-fuel mixture is introduced into the air that is introduced into the combustion working chamber in advance during the scavenging period. Therefore, it becomes possible to perform more complete stratified scavenging, and the amount of air-fuel mixture discharged without being used for combustion, the so-called blow-off amount, is reduced as much as possible to improve fuel efficiency and output It is possible to reduce harmful components in the exhaust gas.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a first embodiment of a two-cycle internal combustion engine according to the present invention at the time of piston top dead center.
2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is an enlarged longitudinal sectional view at the bottom dead center of the piston corresponding to FIG. 1;
4 is a cross-sectional view taken along the line IV-IV in FIG. 3;
FIG. 5 is a longitudinal sectional view at the bottom dead center of a piston showing a second embodiment of the two-cycle internal combustion engine according to the present invention.
6 is a cross-sectional view taken along the line VI-VI in FIG. 5;
7 is a sectional view taken along arrow VII-VII in FIG. 5;
8 is a cross-sectional view taken along arrow VIII-VIII in FIG.
[Explanation of symbols]
1 2-cycle internal combustion engine (first embodiment)
Two-cycle internal combustion engine (second embodiment)
10 cylinders
15 Combustion chamber
18 Crank chamber
20 piston
31 First scavenging passage
32 Second scavenging passage
31a First scavenging port
31e Aperture part
32a Second scavenging port
32e Aperture
32e 'common aperture
34 Exhaust port
50 Air introduction passage
62 Reed valve for air (check valve)
F Longitudinal section of exhaust port
A Air
M mixture

Claims (5)

A longitudinal section (F-F) that divides the exhaust port (34) into two so as to communicate the combustion working chamber (15) formed above the piston (20) and the crank chamber (18) in the cylinder (10). There are provided scavenging passages (31, 31, 32, 32) that symmetrically adopt a Schnure scavenging system, and air (A) is guided to the scavenging passages (31, 31, 32, 32) and the crank chamber ( 18), the air-fuel mixture (M) is guided to the downstream side of the scavenging passages (31, 31, 32, 32) after the exhaust port (34) is opened in the downward stroke of the piston (20). The scavenging ports (31a, 31a, 32a, 32a) provided at the ends are opened, and air (A) is mixed into the combustion operation chamber (15) through the scavenging passages (31, 31, 32, 32) (M ) To be introduced prior to In two-cycle internal combustion engine (1),
The scavenging passages (31, 31, 32, 32) have a plurality of pairs, and each of the plurality of pairs of scavenging passages (31, 31, 32, 32) is throttled near the end on the crank chamber (18) side. Portions (31e, 31e, 32e, 32e) are provided, and each of the throttle portions (31e, 31e, 32e, 32e) is more effective than the downstream portion of each of the scavenging passages (31, 31, 32, 32). The passage cross-sectional area is made narrow and the effective passage cross-sectional areas are made substantially equal to each other, and the size is set such that the air-fuel mixture (M) is fed into the combustion working chamber (15) following the air (A) by a necessary amount. A two-cycle internal combustion engine characterized by the above. The pair of scavenging passages (32, 32) are joined together on the crank chamber (18) side to increase the volume thereof, and the crank chamber (18) is connected via a common throttle portion (32e '). The two-cycle internal combustion engine according to claim 1, wherein the two-cycle internal combustion engine is communicated with the engine. An air introduction passage (50) for introducing air (A) to the scavenging passages (31, 31, 32, 32) is provided, and an air check valve (62) is provided in the air introduction passage (50). The two-cycle internal combustion engine according to claim 1, wherein the two-cycle internal combustion engine is provided. The volume of the scavenging passages (31, 31, 32, 32) is set to be equal to or slightly smaller than the amount of air to be introduced in advance, 2 according to any one of claims 1 to 3. Cycle internal combustion engine. The effective passage cross-sectional area of the throttle portions (31e, 31e, 32e , 32e) is set to such a size that the air-fuel mixture (M) is fed into the combustion working chamber (15) by the required amount following the air (A). The two-cycle internal combustion engine according to any one of claims 1 to 4, wherein the two-cycle internal combustion engine is provided.

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